Electrolytic cell



L. E. WARD.

ELECTROLYTIC CELL.

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Patented Jan. 18, 1921.

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Patented Jan. 18, 1921.

UNITED STATES PATENT OFFICE.

LOUIS E. WARD, F MIDLAND. MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COI- PANY, OF MIDLAND, MICHIGAN. A CORPORATION OF MICHIGAN.

ELECTROLYTIC CELL.

Application filed December 13. 1918.

To wf/ y'ir/w11 9'/ may conccrn:

lic it known that 1, Louis E. WARD, a citizen of the llnited States, and a resident ol hflidiaiid, county of Midland, State of Mi lifran. have invented a new and useful lii'iproveinent in Y[Clecti'olytic Cells, ofwhicli llic` following is a specilcation. the principle of the invention being herein explained. and the best inode in which l have contemplated a'iplying that principle so as to distinguish it froiii other inventions.

'l`lic present iii'iproven'ieiits relate more particularly to electrolytie cells of the soialled tilter press type, which are characterize-fl b v the use of bi-polar electrodes of one lLind or another. this construction permitting tliil passage oiA a current through a series ot cells. or cell coanpartmeits. without the iififessitj-.v olvl separate electrical connections lmiweeii successive cells as in the in lividual type of construction. n electrolytic` apparatus of the type in question is shownt and described in ll. S. latciit No. I Uirllt to Thos. (irisvmld` Jr., dated ugust iii. ltll. aad the present invention may lie regarded iii certain asper ts as an improveinent thereon.

(hie object of the present invention is to provide au improved design of bipolar elecivode. which will facilitate itsy minstrurtioii or assembly in tlie first place. and also its ii'zspectioii and i'epair after installed and in use, while means are also provided whereby :inv desired coll or cells in a series can be rut out :it will without affecting the` operation .of the serie; or apparatus as a. whole. fi Vfurther object is to provide improved means for 'feeding the electroiyte tor` as well :is vf "iwing the saine from. the several ifi-.lis cofiiposiiig the. apparatus. whereby the trolvtii: operation may be independently f-oiitif,ieil in such cells. Still another object is to provide iniliroveil izieans for the collection and removal of the gaseous products of the elcctrolvtic operation.

To the. accoiiiIilisliinent o'i' the foregoing :ind relatrrl enfls. thc iiiveiition,y then`r conv .s ol' the in `ans hereinafter fullyv described sind particularly pointed out in the claims. flic annexed drawings and the following de,` fcriptioi setting forth in detail certain mechanism embodying the invention, such disclosed means constituting. however, but

Specification of Letters Patent.

Patented Jan. 18, 1921.

Serial No. 266,616.

several oi' the various mechanical forms in which the principle of the invention may be used.

ln said annexed drawings l "igure l is a. transverse section of a series ot' cells constituting an olectrolytic apparatus of in v present improved type of construction, the plane, of the section being indicated by the line 1 1, Fig. 2; Fig. 2 is a Yiront elevational view. z'. e. a View of the anode side of one of the component sections or frame of such apparatus; Fig. 3 is a similar elevation of the opposite, or cathode, :fide of such frame or component member; Fig. 4 is a transverse section of such member taken on the plane indicated by the line 4-4, Figs. 2 and 3; Fig. 5 is a similar transverse section of a detail taken on the plane indicated by the line 5-5, Figs. i2 and i3; Fig. 6 is a perspective on a larger scale ol one ol' the individual electrodes carried by such tramo; Figs. 7 and 8 are sectional views of a portion of my improved cell illustratiiig modifications; while Fig. 9 is a diagram showing method of cutting out one or niort` cells.

The eleitrolytic cell or apparatus shown in the aforesaid drawings, it should be eX- plained. is more especially designed for the production ol' caustic and chlorin by the electrolysis of brine` z'. e. sodium chlorid solution: but it will of course be understood that the apparatus is not limited to use in any particular connection, such as that just stated. and that various features thereof may be susceptible of utilization in a number ol' different fields.

fw. in thi` construction of the electrolytic cell or apparatus` which forms the Subject matter of the patent referred to above (No. LUTOALVL the bipolar electrode which characterizes the present construction may be described in a general vay as being a composite one` made b v inserting or otherwise fixing, in a suitable carying member a plurality of bipolar carbon electrodes. In the Following description the term electrode will accordingly be understood to refer to such composite structure. or to the individual eletrode, as the context may require. 'The cariving member may be constructed of any suitablel material adapted for the purpose for which the cell is to be used; thus wood, soapstone, slate, glass, stoneware, or the like, may be used in such construction, or preferably the material employed will be a suitable concrete mixture, since this can be readily molded or cast into the form desired and permit the carrying member to remain in one piece. However, it is not to be understood from this that said members may not be assembled of various parts, nor that the latter may not be of different materials. Thus the surrounding or marginal portion 2a or 2b of the member may be formed or built up separately from the plate or board 1a or 1b which actually carries the electrodes, as illustrated for example in Figs. 7 and 8.

In the preferred construction, however, as illustrated in Figs. 1 to 4linclusive, the carrying member is shown as an integral or one-piece structure, consisting of a fiat plate or board 1 marginally surrounded on-each edge by a raised flange 2, such flange being somewhat deeper on the anode side than on the cathode side. Rising, preferably centrally, from the upper edge of the frame is what may be termed a hollow head 3, which is in communication with the anode side only of the frame through the medium of ducts 4l. This hollow head is also formed in its opposite walls with alined openings 5 forming a passage for the flow of brine located just above the flange 2 which forms the margin of the member, and with a transverse passageway 6 for the iiow of gas in its upper portion separate fromthe chamber 7 within the main portion of the head. Such passageway 6 communicates with the chamber 7 through a duct or opening S and access thereto from the exterior may be had through another opening 9 in the upper edge of thehead, which is normally closed by a cap 10 as shown.

Another smaller head 12, formed with a transverse passage 13, also rises from the upper edge of the frame, the passage in this head communicating with the cathode side of the frame through the medium cof a duct 11i, and being rendered accessible from without through an opening 16 that, like the opening 9 in the larger head, is normally closed with a plug 17.

lf desired (although l have not found it necessary in practicelthe inner surface of the up )er flange on the member on the anode side may incline or slope upwardly slightly from each end of the frame toward the center so that the gaseous product of electrolysis, which collects on this side, will naturally find its way to the chiots 4 and thus escape into the chamber 7 in the larger head. Similarly, the inner surface of the flange on the cathode side of the frame may incline or slope upwardly toward the duct 15,., that communicates with the passage 14 in the smaller head, from the opposite end of the frame, so that thel gaseous product of electrolysis formed on this, z'. e. the cathode, side of the frame will be led to the duct and thence to the passage.

F or withdrawing liquid from the cathode side of the cell, such liquid being of course caustic soda solution where the electrolyte is sodium chlorid brine, as assumed for the purpose ef this description, a tube 2O slidably held in a suitable opening 21 in the bottom iiange of the frame near one end of the latter is provided, the lower end of this tube discharging into and being sealed by a sutable troughlike receptacle 22. Obviously, by vertically adjusting such tube, the height at which the liquid on the cathode side of the frame is maintained may be varied as desired. A separate opening 23 is provided at the opposite end of the frame for withdrawing the liquid on the anode side, if found desirable to drain the corresponding chamber, but this opening is plugged as shown, when the cell is in operation. There is also provided a sight glass 24, which rises vertically above the frame, and communicates at its lower end through a suitable aperture 25 with such anode side, whereby the level of the liquid on this side may be observed, it being understood that such liquid., e. the anolyte, will be maintained at such a height that its level will lie within the chamber 7 in the large head. Means for thus varying the hydrostatic head in the anode compartment are diagrammatically indicated in Figs. 2 and F or the purpose of handling, the frame is further provided with oppositely projecting lugs or pins 26 on its respective ends near its upper and lower edges, whereby it may be picked up by means of a crane, or like transporting means, and carried where desired.

Turning now to the construction of the individual electrodes, these will be seen to consist of approximately cylindrical blocks 80 of graphite, or other suitable form of carbon, preferably of larger cross-section relatively to the total area of the plate or beard 1, in which they are inserted, than are the carbon vpins illust-rated in the aforesaid patent. These blocks will ordinarily be cast in situ, when the frame and board are fomned of concrete, but may be removed and other blocks inserted should this be found necessary during the subsequent use of the apparatus. To the ends of the blocks that project on the anode side are secured flat slabs or plates 31 of the same material as said blocks and preferably of rectangular form., the edges of such plates more or less closely approaching each other, so that the anode, in effect, consists of a large composite carbon plate. The separate plates 31 are ,preferably secured to the corresponding blocks by means of threaded plugs 32 with fiared heads or pins of similar shape driven in place, such plugs or pins being preferably also formed of carbon.

To the cathode ends of the blocks 30 is Secured a metallic (preferably iron) screen 35, such screen being shown as attached to the blocks by means of transversely disposed angle bars 36 welded, or otherwise intimately secured to the screen and then bolted to the adjacent ends of the blocks so as to maintain the screen in good electrical contact with the latter. It will be understood that any other means suited for attaching metal to carbon, such as casting lead about the joint, etc. may be employed. The edges of the screen 35 are received in a shallow recess 37 formed in the adjacent inner edge of the fiange on the frame, and such screen is entirely covered over by means of a porous diaphragm 38 the edges of which are tacked to strips 38 of wood inset in the face of fiange 2. The detailed construction of this diaphragm, like the detailed construction of the screen, is not a matter of interest, having nothing to do with the present invention. A gasket 39 of suitable material is interposed at proper places between the juxtaposed faces of successive frames in the assembled condition of the apparatus, to prevent leakage of either gas or liquid.

It will be seen that the screen 35, and the diaphragm 38 thus supported thereby, lie substantially Hush with the corresponding Jface of the frame, whereas the carbon anode plates 31 lie slightly below, or back, of the corresponding l'ace of the frame. Accordingly, when successive frames equipped with electrodes are brought face to face there will be a narrow space in the anode chamber between the plates and screen, across which the electric current passes through the interposed electrolyte.

In such assembled condition of the parts, the liquid to be electrolyzed is maintained at the desired height in the heads 3 by any suitable means, with the result that the anolyte chambers in which such liquid is first received through the corresponding ducts 4. are all full and under a uniform head throughout the apparatus. As the liquid is electrolyzed, it at the same time percolates through the diaphragm 38 and fills the cathode chamber, c'. e. the space between such diaphragm and the corresponding supporting board 1 or plate, to a height determined by the vertically adjustable tube 20, as previously described. This height, it will be obvious, may be varied in individual cells of the series without respect to the others, in order to secure any desired difference of head between the catholyte and anolyte in each particular cell.

The chlorin which is formed on the anode sides is collected in the chambers 7 in the large heads 3, bubbling up through the liquor that is being fed through said chambers, so as to maintain the same thoroughly mixed, and thence escapes into the passages 6 in the extreme upper portions of the head, these passages being all in communication and so forming a continuous duct through which the chlorin from all the cells is collected and withdrawn. Similarly, the hydrogen arising from the cathode side of successive cells is received and collected in the communicating passages 13 in the smaller heads 12, whence it is conducted away.

Connected with each of the screens 35, which constitutes in effect the cathode meinbers of the several cells, is a bar 40, preterably of copper, which projects upwardly through the corresponding flange of the frame so as to provide an independent electrical connection with the particular screencathode. By attaching a suitable conductor 41 to non-adjacent bars, as shown diagrammatically in Fig. 9, the intervening cathodes, and thus the corresponding cells in their entirety, will obviously be cut out, z'. e. no current will pass therethrough. Such cutting out, or jumping, of one or more cells may thus be secured, whenever a local breakdown occurs, without it being necessary to throw the entire series or apparatus out of commission pending repairs to an individual cell. When a unit is thus cut out, the cap 10 may be raised to permit opening 8 to be plugged, and the chlorin from the cells beyond will thus be carried through passage G without entering the dead cell at all.

It will be understood that by means of the adjustable tube 20 provided for withdrawing the caustic from the cathode side of the cell, the level of such caustic liquor or catholyte within the corresponding cell section, or compartment, may be lowered to any desired degree, and in fact may be run dry; z'. c. the only liquid in the cell will be that in the so-called anode chamber, the caustic being withdrawn as rapidly as formed, as is the practice in most cells of individually operated type. It will thus be seen that my present improved cell, while retaining all of the advantages characteristic of the filter press type of construction, nevertheless permits of operation in substantially the same fashion as does the individual type of cell. In addition, by the improved construction of the composite electrode, it is rendered possible to much more conveniently repair or restore a section of the cell, it ordinarily being necessary merely to replace the wornout sectional plates on the anode side and to put on a fresh diaphragm. By providing means for short-circuiting or cutting out individual cells that may break down, it is possible to keep the series as a whole in operation until the efficiency of the whole apparatus has fallen to the point where it is no longer economical to run the same.

Not only may the plate l be separate from the margin 2 of the carrying member, as heretofore described in connection with Fig. 7, but the marginal flanges may be made separately .from each other as well as from such plate, as shown in F ig. 8. Such anges, in other words, whether integral with the plate, or thus separate therefrom, may be more simply designated as separating members, their function being simply to maintain the parts, more especially the plates and screens, in properly spaced relation, and thereby form chambers or compartments for the retention of the electrolyte.

By the foregoing construction, I am able, in the irst place, to provide a good electrical connection within the apparatus between the anode of one component cell and the metallic diaphragm support that constitutes the cathode of the adjacent cell. 1n the second place, a great-er range of brine headY vupon the diaphragm is secured, than in prevailing constructions, without, however, increasing the external dimensions of the cell. In this way a better control of the brine flow through the diaphragm is renderedA possible. Another advantageous feature is the approximately plane surface of the composite plate anode afforded by the series of separate plates secured to the anode ends of the blocks 3G; this, taken in conjunction with the form of cathode employed, insures a more uniform current density throughout the cell, as well as a lower voltage drop through the cell, than in prevailing types of construction. rFliese plates being detachable, it is possible to renew the anodes in any cell unit, when they become worn, without disturbing the blocks that pass through the carrying member. Finally, one or more units may be easily and quickly cut out, should they become defective, without disturbing the remainder of the apparatus or affecting its operation.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by-any of the following claims or the equivalent of such stated means be employed.

1 therefore particularly point out and distinctly claim as my invention 1. In an electrolytic cell, the combination of two plates supported in spaced relation, the space therebetween being laterally closed to form a chamber for the electrolyte, a metallic screen separating such chamber into compartments, a diaphragm covering said screen, and carbon electrodes projecting through said plates, respectively, one set of electrodes being electrically connected with said screen by direct physical contact.

i-,sesgevtf 2. In an electrolytic cell, the combination of two plates and a separating member secured therebetween, whereby a chamber for the electrolyte is formed, a metallic screen separating such chamber into compartments,

a liapliragm covering said screen, and Carbon electrodes projecting through said plates, respectively, one set of electrodes being electrically connected with said screen by direct physical Contact.

In an electrolytic cell, the combination of two plates supported in spaced relation, the space therebetween being laterally closed to form a chamber for the electrolyte, a metallic screen separatingrsuch chamber into compartments, a diaphragm covering said screen, carbon electrodes projecting through said plates, respectively, one set of electrodes being electrically connected with said screen, and means for adjusting the height of the electrolyte within such compartments.

et. ln an electroyltic cell, the combination of two plates supported iny spaced relation, the space therebetween being laterally closed to form a chamber for the electrolyte, a metallic screen separating such chamber into compartments, a diaphragm covering said screen, carbon electrodes projecting through said plates, respectively, one set of electrodes being electrically connected with said screen, and means for adjusting the height of the electrolyte within such compartments independently of each other.

5. An electrolytic cell comprising two bipolar electrodes, and a separating member secured therebetween, whereby a chamber for the electrolyte is formed, said electrodes each consisting of a carrying member of non-conducting material, blocks of conducting material secured therein so as to project on both sides of the same, and a metallic screen separating such chamber into compartments, one set of blocks being electrically connected with said screen by direct physical contact.

6, An electrolytic cell comprising two bipolar electrodes, and a separting member secured therebetween, whereby a chamber for the electrolyte is formed, said electrodes each consisting of a carrying member of non-conducting material, blocks of conducting material secured therein so as to project on both sides of the same, a metallic screen separating such chamber into compartments, one set of blocks being electrically connected with said screen by direct physical contact, and a diaphragm covering said screen.

7. An electrolytic cell comprising two bipolar electrodes, and a separating member secured therebetween, whereby a chamber for the electrolyte is formed, said electrodes eachV consisting of a carrying member of non-conducting material, blocks of conducting material secured therein so as to project on both sides of the same, a metallic screen separating such chamber into compartments, one set of blocks being electrically lconnected With said screen, a diaphragm covering said screen, and means for adjusting the height of the electrolyte Within said compartments.

8. An electrolytic cell comprising two bipolar electrodes, and a separating member secured therebetween.` whereby a chamber for the electrolyte is formed, said electrodes each consisting of a carrying member of nonconducting material, blocks of conducting material secured therein so as to project on both sides of the same, a metallic screen separating such chamber into compartments, one set of blocks being electrically connected With said screen, a diaphragm covering said screen, and means for adjusting the height of the electrolyte Within said compartments independently of each other.

9. In an electrolytic apparatus of the filter press type, a unit comprising a carrying member of non-conducting material, carbon electrodes secured therein so as to project 0n both sides of the same, and a metallic screen on one side of said member electrically connected with the corresponding ends of said electrodes in direct physical contact.

10. In an electrolytic apparatus of the filter press type, a unit comprising a carrying member of non-conducting material, carbon electrodes secured therein so as to project on both sides of the same, a metallic screen on one side of said member electrically connected with the corresponding ends of said electrodes in direct physical contact, and a diaphragm covering said screen.

1l. In an electrolytic apparatus of the filter press type, a unit comprising a carrying member of non-conducting material, carbon electrodes secured therein so as to project on both sides of the same, a metallic screen on one side of said member electrically connected with the corresponding ends of said electrodes, and carbon plates detachably secured to the opposite ends of said electrodes.

l2. In an electrolytic apparatus of the filter press type, a unit comprising a carrying member of non-conducting material, carbon electrodes secured therein so as to project on both sides ot the same, a metallic screen on one side of said member electrically connected with the corresponding ends of said electrodes, a diaphragm covering said screen, and a plurality of carbon plates respectively detachably secured to the opposite ends of said electrodes.

13. In an electrolytic apparatus of the filter press type, a unit comprising a plate-like carrying member of non-conducting material, a marginal fiange on each side of said carrying member for holding the latter in separated relation when assembled together with other carrying members, a plurality of carbon blocks secured in said carrying member so as to project on both sides of the same, and a metallic screen resting against one of said lianges and electrically connected with the corresponding ends of said blocks in direct physical contact.

i4. In an electrolytic apparatus of the filler press type, a unit comprising a plate-like carrying member of non-conducting material, a marginal flange on each side of said carrying member for holding the latter in separated relation when assembled together With other carrying members, a plurality of carbon blocks secu red in said carrying member so as to project on both sides of the same, a metallic screen resting against one of said flanges and electrically connected With the corresponding ends of said blocks in direct physical contact, and a diaphragm covering the outer face ol said screen.

15. In an electrolytic apparatus of the filter press type, a unit comprising a plate-like carrying member of non-conducting material, a marginal flange on each side of said carrying member for holding the latter in separated relation when assembled together with other carrying members, a plurality of carbon blocks secured in said carrying member so as to project on both sides of the same, metallic screen resting against one of said flanges and electrically connected with the corresponding ends of said blocks, and carbon plates detachably secured to the opposite ends of said blocks.

16. In an electrolytic apparatus of the filter press type, a unit comprising a platelike carrying member of non-conducting material, an integral marginal flange on each side of said carrying member for holding the latter in separated relation when assembled together with other carrying members, a plurality of carbon blocks secured in said carrying member so as to project on both sides of the same, a metallic screen resting against one of said flanges and electrically connected with the corresponding ends of said blocks, a diaphragm covering the outer face of said screen, and carbon plates detachably secured to the opposite ends of said blocks.

17. A series of electrolytic cells made up of a plurality of units each comprising a carrying member of non-conducting material, carbon electrodes secured therein so as to project on both sides of the same, and a metallic screen on one side of said member electrically connected with the corresponding ends of said electrodes in direct physical contact.

18. A series of electrolytic cells made up of a plurality of units each comprising a carrying member of non-conducting material, carbon electrodes secured therein so as to project on both sides of the same, a metallic screen on one side of said member electrically connected with the correspond ing ends of said electrodes in direct physical contact, and a diaphragm covering said screen.

19. A series of electrolytic cells made up of a plurality of units each comprising a carrying member of nonconducting material, carbon electrodes secured therein so as to'project on both sides of the same, a metallic screen on one side of said member electrically connected with the correspond ing ends of said electrodes, and carbon plates detachably secured to the opposite ends of said electrodes.

20. A series of electrolytic cells made up of a plurality of units each comprising a carrying member of non-conducting ma.- terial, carbon electrodes secured therein so as to project on both sides of the same, a metallic screen on one side of said member 'electrically connected with the corresponding ends of said electrodes, a diaphragm covering said screen, and a plurality of carbon plates respectively detachably secured to theopposite ends of said electrodes.

2l. A series ot electrolytic cells made up of a plurality of units each comprising a plate-like carrying member of non-conducting material, a marginal flange on each side oit' said carrying member for holding the latter in separated relation whenA assembled together with other carrying members, a plurality of carbon blocks secured in said. carrying` member so as to project on both sides of the same, and a metallic screen resting` against one of said flanges and electrically connected with the corresponding` ends of said blocks in direct physical contact.

22. A series ot electrolytic cells made up of a plurality of units each comprising a platelilre carrying member of non-conducting material, a marginal flange on each side of said carrying member for holding the latter in separated relation when assembled together with other carrying members, a plurality ot carbon blocks secured in said carrying members so as to project on both sides of the same, a metallic screen resting against one of said flanges and electrically connected with the corresponding ends of said blocks in direct physical contact, and a diaphragm covering the outer 'ace of said screen.

23. A series of electrolytic cells made up of a plurality ot' units each comprising a platelilre carrying member of non-conducting material, a marginal flange oneach side of said carrying member for holding the latter in separated relation when assembled together with other carrying` members, a plurality of carbon blocks secured in each carrying member so as to project on both sides of the same, a metallic screen resting against one of said flanges and electrically connected with the corresponding ends of said blocks in direct physical contact, and carbon plates detachably secured to the opposite ends of said blocks.

24. A series oi electrolytic cells made up oi a plurality of units each comprising a platelike carrying member of non-conducting material, a marginal flange on each side of said carrying` member for holding the latter in separated relation when assembled together with other carrying members, a plurality of carbon blocks secured in each carrying member so as to project on both sides of the same, a metallic screen resting against one of said flanges and electrically connected with the corresponding ends of said blocks, a diaphragm covering the outer 'face of said screen, and carbon plates detachably secured to the opposite ends of said blocks.

25. ln an electrolytic cell of the -lterpress type, a unit comprising a plate-like carrying member ot' non-conducting material, a marginal flange on ,each side of said carrying member ifor holding the latter in spaced relation when assembled together with other carrying members, and a hollow head rising above the upper edge of said member, said head being provided in its lower portion with a transverse passage for the flow of brine and with a transverse pasT sage in its upper portion for the How of gas, the interior of said head being in communication witll both such passages and being connected by a duct through the adjacent flange with the space on one side of said member. y

26. In an electrolytic cell of the filterpress type, a unit comprising a plate-like carrying member of non-conducting material, a marginal flange on each side oi said carrying member for holding the latter in spaced relation when assembled together with other carrying members, a hollow head rising above the upper edge of said member, said head being provided in its lower portion with a transverse passage for the flow of brine and with a transverse passage in its upper portion for the flow of gas, the interior of said head being in communication with both such passages and being connected by a duct through the adjacent flange with the space on one side of said member, and a second hollow head rising above the upper edge of said member. said second head being provided with a transverse passage for the flow of gas connected by a duct throughl such flange with the space on the opposite side of said member.

27. A series of electrolytic cells made up of a plurality of plate-like units each comprising a plate-like carrying member of nonconducting material, a marginal flange on each side of said carrying member for holding the. latter in spaced relation when Yassembled. together with other carrying members, and a hollow head rising above the upper edge of said member, said head being provided in its lower portion with a transverse passage Jor the flow of brine and with a transverse passage in its upper portion for the vflow of gas, the interior of said head being in communication with both such passages and being connectedy by a duct through the adjacent liange with the space on one side of said member.

A series of electrolytic cells made up ol a plurality of plate-like units each comprising a plate-like carrying member oi' non conducting material, a marginal flange on each side of said carrying member for holding the latter in spaced relation when assembled together with other carrying members, and a hollow head rising above the upper edge of said member, said head being provided in its lower portion with a transverse passage for the flow of brine and with a transverse passage in its upper portion for the fiow of gas, the interior of said head being in communication with both such passages and being connected by a duct through the adjacent flange with the space on one side of said member, and means connected with the passages through the lower portions of the heads of said units adapted to supply brine thereto under a variable head.

29. A series ot electrolytic cells made up of a plurality of plate-like units each comprising a plate-like carrying member of nonconducting material, a marginal flange on each side of said carrying member for holding the latter in spaced relation when as sembled together with other carrying mem bers, a hollow head rising above the upper edge of said member, said head being provided in its lower portion with a transverse passage for the flow of brine and with a transverse assage in its upper portion for the flow o gas, the interior of said head being in communication with both such passages and being connected by a duct through the adjacent flange with the space on one side of said member, and a second hollow head rising above the u per edge of said member, said second hea being rovided with a transverse passage for the ow of gas connected by a duct through such flange with the space on the opposite side of said member.

30. In an electrolytic cell of the filter press type, a unit comprising a carrying member of non-conducting material, blocks of conducting material secured to one side thereof, and a metallic screen attached to the other side of said member and directly electrically connected with said carbon electrodes by suitable conductors through said member.

31. In an electrolytic cell of the filter press type, a unit comprising a carrying member of non-conducting material, carbon electrodes secured to one side thereof, and a metallic screen attached to the other side of said member and directly electrically connected with said carbon electrodes by suitable conductors through said member.

Signed by me, this 7th day of December, 1918.

LOUIS E. WARD. 

